Project 1 assesses risk and protective factors related to the specific outcomes of coitus and STI. We propose to address psychosocial factors (e.g., sociocultural and family influences, social/sexual network influences, attitudes and behavior) partner-specific interpersonal relationship factors (e.g., interpersonal communication, reasons for sex and relationship quality) and coitus-specific factors (e.g., sexual interest, mood, senses, substance use that may be associated with risk and protection. Coital diaries and weekly STI screens allow analytic focus on specific coital events. The project is designed as pre-intervention research with the goal of improving understanding of risk factors, protective factors and potential interaction of risk/protection associated with STI among adolescents. Data will be obtained by self-administered questionnaire, by face-to-face interview, by daily reports and by weekly STI screening. Self-administered questionnaires will assess relatively stable attitudes and values, past events and involvement in health-protective and health-harming behaviors. Face-to-face interview will assess partner-specific attitudes, reasons for sex, relationship quality, social/sexual networks and contraceptive/STI preventive behaviors. Daily reports will be obtained during a 12-wee intensive observation period using a daily diary developed from prior research. Daily reports will assess mood, sexual interest, menses, substance use, partner-specific social interactions, coitus and coitus- specific contraceptive/STI preventive behaviors.